The present nested case-control study was designed to investigate whether the association between carotenoid consumption and risk of breast cancer is related to mammographic density. High breast density as measured by mammography has been reported to be a powerful indicator of increased breast cancer risk. The study included 604 breast cancer cases and 626 cancer-free controls in the Nurses' Health Study for whom circulating carotenoid (alpha-carotene, beta-carotene, beta-cryptoxanthin, lycopene, and lutein/zeaxanthin) levels had been measured and mammograms obtained prospectively. Using a computer-assisted method to determine mammographic density, circulating carotenoids were not found to be associated with mammographic density. However, mammographic density significantly influenced the association between total circulating carotenoids and risk of breast cancer (P heterogeneity = 0.008). Total circulating carotenoid levels were found to be inversely associated with overall breast cancer risk (P trend = 0.01). Among women in the highest third of mammographic density, total circulating carotenoids were associated with a 50% lower risk of breast cancer (odds ratio = 0.5; 95% confidence interval = 0.3 - 0.8). Similarly, among these women, high levels of circulating alpha-carotene, beta-cryptoxanthin, lycopene, and lutein/zeaxanthin were found to be associated with a significant 40% to 50% reduction in risk of breast cancer (P trend < 0.05). On the other hand, no such inverse association was observed between circulating carotenoids and breast cancer risk among study participants with low mammographic density. The authors conclude that plasma levels of carotenoids may play a role in reducing risk of breast cancer, especially among women with high breast density.

The present study was designed to examine the chemopreventative properties of chlorophyllin and chlorophyll in a transplacental carcinogenesis model. The authors previously reported that a single 15 mg/Kg dose of the carcinogen dibenzo[a,l]pyrene (DBP) to pregnant mice late in pregnancy caused the offspring to develop an aggressive T-cell lymphoma, as well as lung and liver cancer. In the study, B6129SF1 female mice were bred to 129S1/SvIm males. Beginning at day nine of gestation, the pregnant mice received purified diets incorporating either 2000 p.p.m. chlorophyllin, 2000 p.p.m. chlorophyll, 10% freeze-dried spinach, or no additional supplementation. Lymphoma-dependent mortality was not found to be significantly modified by maternal consumption of any of the special diets compared to control. Similarly, lung tumor burden in mice surviving to 10 months of age was not significantly affected. However, coadministration of chlorophyllin at 380 mg/Kg with DBP by gavage was found to provide significant protection against DBP-induced carcinogenesis. Offspring born to mice receiving chlorophyllin co-gavaged with DBP demonstrated significantly less lymphoma-dependent mortality (P < 0.001). The degree of protection conferred by chlorophyllin (compared to controls dosed with DBP in tricaprylin as the vehicle), was less dramatic, but still significant. Similar coadministration of chlorophyllin also was found to reduce lung tumor multiplicity in the offspring by 50% (P < 0.005). The authors conclude that chlorophyllin can provide potent chemoprotection in a transplacental carcinogenesis model.

The present study determined how cooking influenced in vitro bile acid binding of various vegetables using a mixture of bile acids secreted in human bile under physiological conditions. Greater bile acid binding potential has been associated with lower risk of heart disease and cancer. The bile acid binding capacity of food and food components has been related to their cholesterol-lowering potential. Lowered recirculation of bile acids results in the use of cholesterol in the body to synthesize bile acid and reduced fat absorption. Secondary bile acids have been related to increased risk of cancer. Incubations were conducted for each treatment simulating gastric and intestinal digestion. Cholestyramine (a cholesterol-lowering, bile acid binding drug) was used as the positive control treatment and cellulose as the negative control. Relative to cholestyramine, in vitro bile acid binding on dry matter basis was 13% for the collard greens, mustard greens, and kale; 10% for broccoli; 8% for Brussels sprouts and spinach; 7% for green bell pepper; and 5% for cabbage. These results point to the significantly different (P ≤ .05) health-promoting potential of the vegetables, with collard greens, mustard greens and kale in the top group. Steam cooking was found to significantly improve the in vitro bile acid binding of collard greens, mustard greens, kale, broccoli, green bell pepper, and cabbage compared to the bile acid binding values for these vegetables in raw form. The authors conclude that when consumed regularly after steam cooking, including more of these green and leafy green vegetables would lower the risk of cardiovascular disease and cancer.

The present study compared the anti-cancer activities of betacyanin and anthocyanin plant pigments. Betacyanins and anthocyanins are the most abundant water soluble natural food colorants, whereas lycopene, β-carotene, bixin, and chlorophyll are water insoluble pigments. In the study, betanin, bixin, lycopene, chlorophyll, β-carotene, and cyanidin-3-O-glucoside were isolated from Beta vulgaris (beet), Bixa orellana (annatto), Lycopersicum esculentum (tomato), Spinacia oleracea (spinach), Daucus carrota (carrot), and Prunus cerasus (sour cherry), respectively. These pigments were evaluated, alone and in combination, for their relative potencies against cyclooxygenase enzymes and tumor cell growth inhibition using MCF-7 (breast), HCT-116 (colon), AGS (stomach), CNS (central nervous system), and NCI-H460 (lung) human tumor cells. Among the pigments tested, betanin, cyanidin-3-O-glucoside, lycopene, and β-carotene were found to inhibit lipid peroxidation. However, all the pigments resulted in COX-1 and COX-2 inhibition and demonstrated a dose-dependent growth inhibition against breast, colon, stomach, central nervous system, and lung tumor cells. In further testing, combinations of the pigments were investigated for their synergistic effects and chemical interactions at various concentrations. The mixture of anthocyanin and betanin was found to cancel out their individual efficacy in the cell growth inhibitory assay and did not enhance the COX enzyme inhibitory activity.

The current study was designed to investigate the activities of glycolipids in human cancer cells. The major glycolipids in monogalactosyl diacylglycerol, digalactosyl diacylglycerol and sulfoquinovosyl diacylglycerol (SQDG) were purified from dried vegetables. The glycolipids together were found to inhibit DNA polymerase alpha (pol alpha) activity in vitro. DNA polymerase alpha activity is elevated in breast cancer, among others. The glycolipids were also shown to reduce proliferation of human cancer cells. To study the potential anti-cancer effects of the glycolipids in vegetables, eight selected vegetables were investigated to determine their glycolipids content, mammalian DNA polymerase inhibitory activity, and antiproliferative activity. Green tea was found to possess the greatest amount of glycolipids overall. Spinach had the most SQDG, followed by parsley, green onions, chives, sweet peppers, green tea, carrots and garlic. Spinach was found to have the strongest inhibitory effect on pol alpha activity and cancer cell proliferation. In fact, a significant positive association was found between SQDG content and inhibition of DNA polymerase. Further testing of six subspecies of spinach demonstrated that "Anna" had the most SQDG. The authors conclude that, based on its strong inhibitory activity against human cancer cell proliferation, the glycolipid fraction from spinach is potentially a source of anticancer activity.

The current study evaluated the phenolic profiles and antioxidant and antiproliferative activities of 10 common vegetables. The vegetables were selected on the basis of per capita consumption in the U.S. Broccoli was found to have the highest total phenolic content, followed by spinach, yellow onion, red pepper, carrot, cabbage, potato, lettuce, celery, and cucumber. Red pepper was found to have the greatest total antioxidant activity, followed by broccoli, carrot, spinach, cabbage, yellow onion, celery, potato, lettuce, and cucumber. The phenolics antioxidant index was used to evaluate the quality and quantity of phenolic contents in these vegetables and was calculated from the corrected total antioxidant activities by eliminating the contribution of vitamin C. Antiproliferative activities were evaluated using HepG(2) human liver cancer cells. Spinach was found to have the highest inhibitory effect on proliferation, followed by cabbage, red pepper, onion, and broccoli. On the basis of these results, the authors proposed a bioactivity index for dietary cancer prevention to provide a simple reference for consumers to choose vegetables in accordance with their beneficial activities.

In the current study, 198 Mexico City women aged 21 to 79 years with breast cancer were individually age matched to 198 women with no breast disease from 1994 to 1995. Information on socioeconomic characteristics and diet was obtained by interview and a questionnaire was used to estimate the level of consumption of 95 foods. The effect of selected foods on risk of breast cancer was estimated using logistic regression models. The adjusted odds ratio for the consumption of more than one slice of onion per day and breast cancer was 0.27 (95% confidence interval = 0.16-0.47), and had a statistically significant trend (p < 0.001). This protective effect remained after adjustment for known breast cancer risk factors. For premenopausal women, there was also a protective and significant effect associated with the intake of lettuce and spinach and nonsignificant protective effects for apples and herbal tea.

The present population-based case-control study was designed to examine the associations between intake of carrots, spinach, and vitamin A in supplement form, and risk of breast cancer. Nine questions on food and supplement intake were used to assess intake of beta-carotene and vitamin A. The study was conducted in Maine, Massachusetts, New Hampshire, and Wisconsin during the period 1988 to 1991 and included 3,543 breast cancer cases and 9,406 cancer-free controls. Compared to no consumption of carrots or spinach, eating carrots or spinach more than twice weekly was found to be associated with a significantly lower risk of breast cancer (odds ratio = 0.56, 95% confidence interval: 0.34-0.91). However, no trend was found for estimated intake of preformed vitamin A from all evaluated foods and supplements. The authors commented that the data did not enable them to distinguish among possible explanations for the protective association observed between intake of carrots and spinach and risk of breast cancer.